There is a related art relating to a seating determination apparatus configured to determine a seating state of a vehicle seat in comparison of a seat load on the basis of outputs from load sensors configured to detect a load of a passenger or the like seated on a seat cushion portion of the vehicle seat with a predetermined threshold value (For example, see JP 9 207638A).
The positions of installation of the load sensors are two positions out of four corners of the seat cushion portion which are apart from each other in the fore-and-aft direction and the left-and-right direction of a vehicle, which are minimum required positions including one position on the rear side. The two positions include the front and the rear in the same left-and-right direction, or the front and the rear in the direction of diagonal lines of a square formed by connecting the four corners.
The seating state of the vehicle seat determined by the seating determination apparatus is used for controlling an operation of an airbag apparatus. In other words, the airbag apparatus is controlled to be an operation-permitted state when it is determined to be an adult-seated state, which is a state in which an adult is seated on a vehicle seat for a passenger seat, and to be an operation-prohibited state when it is determined that no passenger is seated on the vehicle seat or to be a child-seat-fixed state in which a child is seated on a child seat.
In recent years, vehicles are becoming more multifaceted toward higher comfort, and as regards a reclining mechanism configured to change the angle of a seatback portion of a seat or a lifter mechanism configured to change the height of the seat cushion portion, for example, to be mounted on the vehicle seat, the seatback portion or a headrest portion, which are movable portions of the seat, have wider movable ranges in a vehicle cabin. As a result of lowering of a vehicle height in order to reduce a traveling resistance, a ceiling portion in the vehicle cabin is also lowered.
However, determining the seating state on the vehicle seat simply in accordance with a seat load on the basis of a load applied on a rear portion of the seat cushion portion of the vehicle seat is often associated with a problem. As described above, since the movable range of the vehicle seat is increased, interference areas in which the vehicle seat interferes with interior members disposed in the vehicle cabin are also increased. Therefore, if the height of the seat cushion portion is increased by the operation of the lifter mechanism which is capable of changing the height of the seat cushion portion after it is determined that no passenger is seated on the vehicle seat or to be a child-seat-fixed state in which a child is seated on a child seat for example, since the height of the headrest portion located on a top portion of the seat is also increased and, when the seatback portion of the seat is moved toward an upright position by the operation of the reclining mechanism which is capable of changing the angle of the seatback portion, the height of the headrest portion located above the seatback portion is also increased. Consequently, the headrest portion interferes with a ceiling inner wall member, which is the interior member, arranged on the ceiling portion of a cabin and is pushed against the ceiling inner wall member, so that a compression load acts on the load sensor located on the rear portion. In this case, on the vehicle seat, since the compression load corresponds to an increased load, the seat load is increased beyond a threshold value, and hence it may be determined that the state is transferred from the child-seat-fixed state (the airbag apparatus is in an operation-prohibited state) to an adult-seated state (the airbag apparatus is in an operation-permitted state) erroneously even though an adult is not seated.
In a case where the seatback portion of the seat is reclined rearward by the operation of the reclining mechanism after the determination as the adult-seated state, the headrest portion located above the seatback portion interferes with a seat cushion portion of a rear seat, and is pushed against the seat cushion portion so that a tensile load acts on the load sensor on the rear portion. In this case, in the vehicle seat, since the tensile load corresponds to a reduced load, the seat load is increased beyond the threshold value, and hence it may be determined that the state is transferred from the adult-seated state (the airbag apparatus is in the operation-permitted state) to the child-seat-fixed state (the airbag apparatus is in the operation-prohibited state) erroneously even though the adult is seated.
Therefore, a seating determination apparatus configured so as not to be associated with drawbacks as described above is desired.